1. Field of the Disclosure
The present disclosure relates generally to an electronic device including a touch sensor including a fingerprint recognition (or fingerprint verification) in the electronic device and a method of driving the touch sensor.
2. Description of the Related Art
As use of electronic devices such as a smart phone, a tablet PC, and a wearable device is generalized, a concern about security and the usability of the electronic device increases. In fact, the security and the usability has a trade-off relationship, and thus it is normal that the usability is reduced while the security is increased. However, if a two-dimensional (2D) fingerprint sensor is installed together with a display in an electronic device, a usability of fingerprint recognition, which already provides high security, may be improved innovatively. A user experience of a normal touch using a touch screen panel (TSP) and that of a touch for a fingerprint recognition are organically connected with each other, and thus the security and the usability may be simultaneously ensured.
As described above, the 2D fingerprint sensor capable of recognizing the fingerprint in the display is an innovative technology, but there are many technical considerations in implementing the 2D fingerprint sensor. The most prominent are a fingerprint recognition rate and a large current consumption.
The fingerprint sensor installed in the electronic device recognizes a shape of the fingerprint in a swipe method or a touch method, and compares the recognized fingerprint with previously generated fingerprint data to authenticate the fingerprint. In order to recognize the shape of the fingerprint, valleys and ridges of the fingerprint should be determined. In the determination of the valleys and the ridges, various methods are used, and optical, ultrasonic, capacitance methods, and the like are used.
Among these, the capacitance method is frequently used in an electronic device such as a smart phone and a tablet PC. A sensor for a fingerprint recognition in the capacitance method includes a transmitter electrode (line) (Tx) and an receiver electrode (line) (Rx). Specially, the Rx is formed in a dense interval for the fingerprint recognition. When a user touches a fingerprint sensor formed of the Tx and Rx, a charge is transmitted from the Tx to the Rx, and a value of the capacitance received by the Rx is changed according to a distance between a finger and the Tx. Since this value is inversely proportional to a distance, the valleys and the ridges of the fingerprint may be generated based on this.
The fingerprint sensor using the capacitance may be defined as a one-dimensional (1D) or 2D fingerprint sensor according to a method of forming the Tx and the Rx. The 1D fingerprint sensor is commonly referred to as a shape of sweeping a finger, that is a swipe method, and the 2D fingerprint sensor is referred to as a shape of pushing the finger, that is a touch method.
The fingerprint sensor may be vertically combined with a touch screen, or may be formed in parallel with the touch screen. Therefore, an operation and a recognition of the fingerprint sensor may be simultaneously performed while operating a touch screen.
However, in the conventional design of a fingerprint sensor combined with a TSP which is an input means of the touch screen, there may be the following problems.
First, a cost increase resulting from an increase to a screen size may occur. The fingerprint sensor should accurately scan a shape of the fingerprint of a finger differently from a capacitance type touch screen. For example, the fingerprint sensor may have Tx and Rx distances of 50 μm. Tx and Rx distance formations of a considerably dense interval-type are necessary in this process.
A screen of an electronic device such as a smart phone has a tendency to be large, and thus when a fingerprint sensor corresponding to the size of the screen is included in the electronic device, a cost is naturally increased according to the size of the screen. However, although the screen of a tablet PC may be larger than a screen of a smart phone, the Tx and Rx distances of the fingerprint sensor should be the same as those of the smart phone.
Next, a confusion between a touch of the touch screen and a touch of the fingerprint sensor may occur. When the fingerprint sensor is installed in the uppermost side, the lowermost side, the leftmost side, and the most rightmost side of an electronic device screen, a conflict related to a user experience (UX) may be generated between a normal touch operation and a fingerprint recognition operation. For example, when a fingerprint input is allowed in an upper side notification panel area and a button input area of a lower side, the fingerprint recognition operation may conflict with the touch operation. In addition, in a case of a multi-touch operation, a UX between the normal touch operation and the fingerprint touch operation may become complex.
Accordingly, there is a need to distinguish between a touch input and a fingerprint input. Thus, a separate fingerprint input mode may need to be provided. When a separate fingerprint input mode is provided, a partial fingerprint input may be possible without a need to enable a fingerprint input in a whole screen.
Additionally, a difficulty of the fingerprint recognition in a curved screen of the electronic device may occur. The fingerprint recognition is not uniform in the curved screen, and thus the fingerprint recognition in the touch operation may be difficult.
Finally, a large current consumed in the case of the fingerprint recognition may occur. In the case of the fingerprint recognition, both the TSP and the fingerprint sensor must be operated. When the fingerprint sensor is formed of the Tx and the Rx in a whole screen, all Tx and Rx should be turned on for a partial recognition since it is not known where to recognize the fingerprint.
Accordingly, a new structure for a fingerprint sensor installed in a portable electronic device having a TSP, such as a smart phone, a tablet PC, and a wearable device (or wearable apparatus) is needed.